Sigma 14mm f/1.8 DG HSM Art Lens Review

Sigma has been breaking ground with many lenses in their Art series and the review-time-latest groundbreaker is this one, the Sigma 14mm f/1.8 Art Lens.
The big deal this time?
While there are numerous lenses covering the 14mm focal length available, no full frame lens wider than 20mm (another Art lens) has an aperture this wide.
Astrophotographers everywhere were drooling the day this lens was announced.
The promise of the high-grade optical and build quality of a Sigma Art lens combined with an ultra-wide angle focal length's ability to take in a great amount of the sky while keeping both the stars and an included foreground sharp in addition to the especially-needed widest-ever aperture were exactly what they have been longing for.

While not everyone is interested in the astrophotography capabilities of this lens, everyone will like the features that make it a great lens for night sky photography.
One of these features is the wide angle focal length, one able to keep both near and distant subjects in focus even at an ultra-wide aperture.
That a lens has an ultra-wide aperture is not enough – it must deliver excellent image quality at that wide aperture and this one completely, impressively fills in that check box.
The balance of the feature set seals the deal: great build quality, great looks, great features and, for the specs of this lens, I think it has a worthy price.

Focal Length

A primary reason to want this lens is because it has a 14mm focal length, and the focal length will largely determine the types of photography this lens is used for.
The ultra-wide 114° angle of view presented by the 14mm focal length is both very useful and extremely fun to use.

As already alluded to, this lens is an excellent choice for photographing the night sky.
The 14mm angle of view takes in a large portion of the sky and, with a correspondingly-deep depth of field, it is easy to keep both stars and foreground subjects in sharp focus, even at f/1.8.
The wide angle of view creates rather small stars, but with the low magnification, the earth's rotation does not cause them to become blurred in images captured at longer exposures, meaning that lower, less-noisy ISO settings can be used.

I couldn't wait to introduce this lens to a clear, dark sky and did so at the first chance I got.
And, with each darker, clearer night sky, I went back out.
My wife surely thought I was avoiding her, but ... the Perseid meteor shower was taking place and ... the more images I captured, the more meteor streaks I obtained.

I should warn you, photographing the night sky is very addicting and for all good reasons.
If you are not already addicted, you need to try this.
Find a dark sky on a dark night and be there with this lens.

Photographing architecture is another popular use for a 14mm lens.
Buildings are big and working space is often limited by other buildings, trees, power lines, etc., making an ultra-wide angle focal length such as 14mm a requirement for the task.
Remember that technical architecture photography often requires a level camera (or a tilt/shift lens) to keep vertical lines from converging.
It is often hard to gain a mid-building height vantage point for such photography, but an ultra-wide angle lens will often permit the entire building(s) to be included in a ground-level image captured with a level (both tilt and roll) camera.
Any unwanted foreground can simply be cropped away.

Interior photography is another scenario where working space is frequently limited and a wide angle of view is needed to capture the entire space.
A benefit from using an ultra-wide angle focal length for both interior and exterior real estate photography is that the angle of view makes spaces appear larger and larger is typically desired in this field.

One of the most-common uses of 14mm is in landscape photography.
The outdoor world is full of wide angle scenes awaiting your shutter release behind a 14mm lens.
Wide angles are especially good for making foreground landscape subjects appear large in relation to background subjects (due to perspective) while enabling the inclusion of a vast background both in the frame and in-focus.
When out and about, look for interesting subjects with interesting backgrounds.
Then move in close for the ultimate image, providing the viewer a strong sense of presence in the image.

Nightscapes are of course included in the 14mm capabilities, but I'll also add cityscapes to the list.

I wanted to make this art sculpture, located in front of the Maryland Science Center, large in the frame with Baltimore's Inner Harbor and a colorful sky at sunset forming the background.
This focal length worked excellently for that task.

Creating a multi-shot panorama is a common technique used for photographing landscapes.
Panorama image capture permits a wider overall angle of view to be recorded than a lens is otherwise capable of.
Very wide angle focal lengths can capture a big scene in one frame and can provide a panorama look (wide aspect ratio) by simply cropping the top and bottom from a single image capture.
While the multi-image pano can create an even higher resolution final image, that resolution may not be needed with today's ultra-high resolution cameras and cropping is much easier than stitching.

Try directing this lens straight upward while in a forest.
Lay on your back amidst interesting tall trees for an easy-to-capture composition that, with each tree trunk becoming a leading line into your frame, looks great.

While considering this lens for landscape photography use, it must be understood that the 14mm Art lens' beautiful convex front lens element precludes the use of standard threaded front filters, namely the
circular polarizer and neutral density filters commonly used for landscape photography.
Companies such as Fotodiox design filter solutions for these types of lenses, but the filter holder and the filters themselves are quite large.
It should also be noted that a slip-in rear gel filter holder, useful for holding neutral density gel filters, is not provided.
Update: Sigma has announced that the Rear Filter Holder FHR-11 can be optionally installed on this lens either by yourself or by Sigma (for a service fee).
Regardless, there remains a lot of landscape photography to be done without filters.

A 14mm lens can be a good choice for going underwater, allowing even larger subjects to be framed from close distances that avoid water clarity issues.
While I would have prefered the opportunity to be in the water while photographing under the surface level, I opted for the next-best (and much less expensive) alternative: the National Aquarium in Baltimore.

Note that the ultra-wide angle of view through thick, flat acrylic aquarium walls means that light reaching the camera from hard angles is unevenly diffracted, causing strong blur in the frame borders.
So, use this illustration for true underwater photography purposes where an underwater housing dome will properly transmit light with completely sharp results obtained.

The 14mm focal length, especially with the interesting perspective it provides, can capture artistic imagery.
Take advantage of perspective distortion by moving in close to make something appear huge in relation to its surroundings.
For example, hold the small fish you caught close to the camera to make it appear huge, backing up your "big fish" story.
Use caution when including people in the 14mm frame as the just-referenced perspective distortion may not be appreciated for portraiture.

Not only does Mikayla's face show perspective distortion at this close distance (see the differently-sized eyes?), the close camera-to-face distance caused her to distort her own face due to the uncomfortable lens proximaty.
Incidently, this image was captured at near minimum focus distance with f/1.8 selected.
Thus, it shows both the maximum magnification and the maximum background blur this lens can produce.

Back up and a 14mm lens can be a great choice for portraiture.
In the following example, we see the interior of the restaurant where Mikayla and I ended our daddy-daughter day in Baltimore.

Mikayla is obviously the focus of the image, but the background tells the story.
Here is another example of an environmental portrait.

When you need to back up farther, but simply can't, 14mm might be the right choice.

Considerations must be made when using a 14mm focal length with flash as most do not natively cover an angle of view this wide.
A diffuser (either built in or accessory) or bounce flash (or similar) will be required to avoid a partially-lit scene.

The Sigma 14mm f/1.8 Art Lens is a full frame lens and though the above discussion focuses on this lens being used on a full frame camera, it also has great uses on smaller-sensor APS-C
(1.5x/1.6x FOVCF) cameras.
With their smaller imaging sensor size using only the center portion of the image circle, APS-C cameras provide a narrower angle of view, similar to that of a 22mm lens on a full frame body.
While the 22mm-like angle of view is considerably less extreme (falling between the 20mm and 24mm examples above), many of the uses are the same.
Even with far more APS-C options available to cover the 14mm focal length, none offer the highly-desireable f/1.8 max aperture of this lens.

Max Aperture

At review time, the max aperture in the Sigma 14mm f/1.8 Art Lens is 2/3 of a stop wider/faster than the widest full frame alternative, the Irix 15mm f/2.4 Blackstone Lens.

What is the wide aperture good for?
Stopping action, that of either a subject in motion or a camera being handheld, in low light is an especially great benefit of this feature.
At the low magnification of the 14mm focal length, many photographers can get away with an f/2.8 or f/4 max aperture lens for much/most of their work.
However, there are many scenarios where f/1.8 can make a big difference, especially in the ISO setting needed to achieve the same image brightness.

I already mentioned the night sky scenario where the earth's rotation becomes fast action relative to the dim-ness of the night sky.
Low light events, especially weddings, are another great use of f/1.8.
Being able to reduce the ISO setting to 1 1/3 stop lower than when using an f/2.8 lens can mean ISO 2500 instead of ISO 6400, with a noise level difference being very noticeable.

Not immediately obvious to everyone is that when a lens can be stopped down to match the widest aperture of a slower lens, the wider lens usually has less vignetting and this
difference can be huge (about 3 stops in that example).

A highly valued wide aperture benefit is the ability to create a strong background blur.
While wide angle lenses do not magnify the background enough to blur its subjects beyond recognition, it can create enough separation from a close subject to make it stand out amidst a distracting background.
Use the images of Mikayla at the restaurant (above) for an example of this.

A wide aperture means a bright viewfinder, which is especially helpful in low light, and a wide aperture can aid in a camera's low light focusing capabilities/precision.

The downsides to a wide aperture, primarily because of the larger lens elements required, include larger physical size and a higher price tag.

Also note that, especially under full sun conditions, a 1/8000 shutter speed may be only marginally fast enough to avoid blown highlights at f/1.8.
Cameras with shutter speeds limited to 1/4000 may need the assistance of a neutral density filter to keep images dark enough at f/1.8 (as previously noted, a third-party solution or installation of the rear filter holder would be required for ND use).
Shooting with a narrower aperture of course remains an easy alternative, but the background blur will be reduced accordingly.

Image Quality

Image quality always matters highly and with the wide aperture being such a prominent feature of this lens, "How sharp is the Sigma 14mm f/1.8 Art Lens wide open?" was the big question many of us wanted answered first.
And, the lab-test results immediately produced a "Wow!" answer to that one.

Wide open at f/1.8, this lens is very sharp in the center of the frame.
At f/2, a slight increase in contrast and resolution is seen and another slight increase of the same at f/2.8 brings on the definition of "extremely sharp".

Taking the testing outdoors, we next look at a pair of center-of-the-frame 100% resolution crop examples.
These images were captured using an ultra-high resolution Canon EOS 5Ds R with RAW files processed in Canon Digital Photo Professional using the Standard Picture Style and sharpness set to only "1" (0-10 scale).

As is so often the case, the outdoor results match our lab tests with sharpness being quite good at f/1.8 (even with only very light sharpening) and improving slightly at the two next full-aperture stops.
I didn't include or talk about f/4 results because ... the f/2.8 results are amazing and you will not likely notice any difference at f/4.

An ultra-wide angle lens with an ultra-wide aperture immediately draws expectations for soft corner-of-the-frame performance, at least at the widest apertures.
But, I am happy to inform you that isn't the case with the 14mm Art lens.
While improvement is seen by stopping down through f/4, corner performance even wide open is still good.
Here are two sets of examples showing 100% crops taken from the absolute corner of 5Ds R images captured and processed the same as the above examples.
You are looking at the bottom-left corner first, followed by samples from the bottom-right corner.

Landscape photographer especially will love these corners.
There was no reason to show you f/5.6 examples as the f/4 corners are extremely good.

I saw no discernable difference between any of the four corners to indicate an alignment issue and focus shift is similarly not an issue.

A wide angle lens with a widest-ever aperture is going to show worst-ever peripheral shading, right? Wrong.
While the just-over-3 stops of vignetting at f/1.8 is noticeable in full frame corners, this amount is similar to or better than the best of this lens' peers at f/2.4 or f/2.8.
Stop this lens down only 1/3 stop to f/2 and nearly a stop of the corner shading goes away and at f/2.8, only about 1.5 stops remains.
At f/5.6, just under 1 stop (the amount often used as the boundary for visibility) remains and this amount continues throughout the remainder of the narrower apertures.

APS-C-format camera owners will see around 1 stop in the f/1.8 corners and practically none at the narrower options.

As I have repeated many times, if lens elements refracted all visible wavelengths of light identically, a lens designer's job would be a lot easier.
Because they do not, we get aberrations caused by various wavelengths of light being magnified and focused differently.

Lateral (or transverse) CA (Chromatic Aberration) is an imperfection I readily notice.
This shows as different colors of the spectrum being magnified differently with the mid and especially the periphery of the image circle showing color fringing along lines of strong contrast running tangential (meridional, right angles to radii), where the greatest difference in the magnification of wavelengths exists.
While lateral CA is usually easily corrected with software (often in the camera) by radially shifting the colors to coincide, it is of course better to not have it in the first place.
And, since this lens will be used mostly on non-Sigma brand cameras, it is extremely unlikely that camera manufacturers will load the required lens correction profile in their cameras.
That means lateral CA correction is not available for JPG format image capture and that this CA will be recorded in videos.

Let's look at a worst-case example (100% crop from an extreme corner of an ultra-high resolution 5Ds R frame).
This is the top left corner.

There should be only black and white colors in the image above with additional colors revealing lateral CA.
The good news is that there is very little lateral CA showing here and an especially low amount for a lens with a focal length this wide.

A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light, or more simply, different colors of light are focused to different depths.
Spherical aberration along with spherochromatism, or a change in the amount of spherical aberration with respect to color (looks quite similar to axial chromatic aberration, but is hazier) are other common lens aberrations to look for.
Axial CA remains at least somewhat persistent when stopping down with the color misalignment effect increasing with defocusing while the spherical aberration color halo shows little size change as the lens is defocused and stopping down one to two stops generally removes this aberration.

In the real world, lens defects do not exist in isolation with spherical aberration and spherochromatism generally found, at least to some degree, along with axial CA.
These combine to create a less sharp, hazy-appearing image quality at the widest apertures.

The following example shows a neutrally-colored subject in the background (behind the plane of sharp focus) and in the foreground.
These are 100% crops.

What we see in this example is that there are some mild highlight fringing color differences, but nothing too bad here.

When using an ultra-wide angle lens, it is not hard to get the sun in the frame and the sun is one of the best sources of lens flare available.
Even with the sun in the corner of the frame, this lens shows only a small amount of flare effects at f/16 and minimal flare effects are present at wider apertures for a very impressive performance.

Coma is generally recognized by sharp contrast towards the center of an image and long, soft contrast transition toward the image periphery.
Coma becomes quite visible mid-frame and in the corners of images captured at wide apertures and significantly resolves when the lens is stopped down.
Astigmatism is another lens image quality attribute that is often apparent in the corners and the pin-point stars in the night sky are a subject that makes these aberrations, along with some others, most easily recognizable to me.

As this lens appeared to be the ultimate wide angle astrophotography lens, I couldn't wait to put some stars in the corner of the 14 Art's frame.
With increasingly darker and clearer skies, I went out five different evenings, hoping for improved results each time, hoping that I was perhaps slightly mis-focusing.

Corner results from the best image of each of the first four nights are shown above, and on the fifth night, I used an equatorial tracking mount.
The 5th night tracking mount results simply confirmed the other results.
While these results are relatively good in comparison with this lens' peers, there are still wings on the corner stars.

From a geometrical distortion perspective, this lens shows some of the barrel variant.
The amount is not extreme and the effect is rather even (vs. a mustache/wave pattern), but if straight lines are running near and parallel to the frame borders, the curvature will be noticed.

Most modern lenses have lens correction profiles available for the popular image processing software programs and distortion can be easily removed using these, but distortion correction is destructive at the pixel level and
this technique is seldom as good as using a distortion-free lens in the first place.
Again, non-Sigma cameras will not provide lens distortion in-camera for Sigma lenses, meaning that it will show in JPG-format images and in movies.

Bokeh, the quality of the background blur, is not as big of a concern with an ultra-wide angle lens as it is with longer focal length lenses, but this lens appears to create a nice quality blur even when stopped down to f/8, where the aperture blades are greatly affecting the blur quality.

As the aperture gets narrower, point light sources take on a starburst effect and often I find that the wider the max aperture of the lens, the stronger the star effect a lens can produce.
The 9-blade aperture creates 18-point stars as seen below.

The Sigma 14mm f/1.8 Art Lens' optical score takes a ding from the modest barrel distortion and some coma/astigmatism showing in the corners, but it is otherwise a stellar performer in this regard.

Focusing

Like the rest of the Art lenses hitting the street to date, the 14mm Art Lens gets Sigma's best AF system, HSM (Hypersonic Motor).
At normal focus distance changes, AF locks on the subject nearly instantly.
Do a full extent AF adjustment, from near minimum focus distance to infinity or vice versa, and you can easily watch the lens make its adjustment.
Quiet focusing is normal for HSM systems and this one again meets that expectation with just a "shhhh" of the lens elements/groups moving during AF.

Despite the relatively deep depth of field provided by the 14mm focal length not stressing an AF system to keep subjects within the deep depth of field, this lens still does not come close to what I consider "good" in terms of consistent AF accuracy and the peripheral AF points did not perform as well as the center AF point.
That is of course not what I wanted to have to tell you here, but ... that is my experience with this lens and have tripod-tested it over and over again on a pair of EOS 5Ds R bodies and an EOS 1D X Mark II with similar results delivered by all three.
Live view (or an EVF) type AF provides a much better accuracy experience and at this wide of an angle, manual focusing is often an easy option.

While AF consistency cannot be calibrated, focus calibration can be adjusted (in detail) using the Sigma Dock (more about this later).

As usual for Sigma HSM implementations, internal focusing is featured and FTM (Full Time Manual) focusing is enabled.
Both are nice features commonly found on quality lenses.

The 14's effective focal length changes modestly with focusing, causing subjects to change size slightly as the focus ring is turned.
Focus, establish framing and then tweak focusing to perfection for a critically-framed image.

The 14 Art's manual focus ring is very nice.
It is smooth, has no play and has an ideal amount of rotation for precise manual focusing even with very close subjects.
The location of this ring encompassed the entire rear portion of the wide front section of the lens (a location similar to that of the Sigma 12-24mm Art Lens focus ring).
The focus ring is nicely-sized (larger than the 12-24 Art lens' MF ring), very easy to find and inherently quite wide in diameter.

The 14mm Art lens' 10.6" (270mm) minimum focus distance produces a very-meager 0.10x maximum magnification.
This spec lands this lens near the bottom of the chart of 14 or 15mm-capable lenses.
While a higher spec would be nice, it would not be very practical to decrease the minimum focus distance because, at MFD, there is currently only about 2.5" (63mm) of working space in front of the hood.

As shared in the distorted portrait sample picture above, at this lens minimum focus distance, the ultra-wide angle perspective distortion effect can be established.

Often, a lens' minimum focus distance can be reduced via extension tubes.
However, on lenses this wide, even a 12mm extension tube reduces the minimum focus distance too much to be usable.
With the lens focused to infinity, the maximum focus distance with the 12mm ET is against the front lens element.
To be usable at that focus distance, the subject would need to be lit from behind and if you need that much magnification, this isn't the right lens for the purpose.

Build Quality & Features

With the Global Vision series, Sigma introduced a modern, classy-looking, tightly-dimensioned, high-quality design for their lenses.
From the aesthetic mix of matte and gloss black finish to the great-feeling sharply ribbed rubber rings to the nicely-shaped overall dimensions, the Art lenses all have very impressive design qualities.
And, looking and feeling great lends to a high fun-to-use factor.

While this lens, appearing very similar to the Sigma 12-24mm f/4 DG HSM Art Lens including the large convex objective element, has a somewhat unique shape, it still appears to fit in with the rest of the Art-designated lens family.

The image above shows these two just-referred-to lenses side-by-side with their shared design elements being obvious.

This is a fixed-size lens with the focus ring and AF/MF switch being the only external moving parts.
As mentioned, the focus ring is easy to find and performs very nicely.
The AF/MF switch is conveniently positioned on a slightly raised switch bank.
As standard with Global Vision lenses, the back of the switch shows white when in the auto position.

The lens hood, nicely-protecting the large convex front lens element, is built-in and non-removable.

Like many of the Sigma Art lenses being introduced at this time, the lens barrel construction material of choice is a Thermally Stable Composite (TSC) material, used for greater precision and for better-handling wide temperature variations, with traditional metal components also being utilized.

As this is a lens that will be frequently used outdoors, that it has weather sealing is highly appropriate and desirable.

Weighing in at 41.3 oz (1170g) and measuring 3.8 x 5.0" (95.4 x 126.0mm), the Sigma 14mm Art lens does not gain entry into the lightweight club.
It is only .4 oz (10g) away from equaling the heaviest lens in the chart below.
Still, especially considering the ultra-wide aperture, this lens' size and weight are in line with expectations.

Commonly provided with lenses having integrated hoods is a lens cap that also covers the sides of the hood and that lens cap style is provided with the 14mm Art lens.
This cap uses a friction fit via a thin ring of flocking-like material inside the hood.
While staying attached is problematic for some of these caps, this one, similar to the Sigma 12-24mm Art Lens cap, has been holding on nicely.

The Sigma 14mm Art Lens arrives in a nice zippered padded nylon case with a shoulder strap, though without a belt loop.

Sigma Global Vision and the USB Dock

Sigma's Global Vision lenses get a classification of "A", "C" or "S", representing a primary Sigma-intended use of "Artistic", "Contemporary" and "Sports".
A full description of these categories can be found in the Sigma 35mm f/1.4 Art Lens press release.

Don't read too much into the category names (they are too limiting), but Sigma has been introducing some very nice lenses under all 3 names.
This of course is an "Art" lens and as such, gets an "A" stamped in a classy chrome circle on the lens barrel.

A great feature of the Global Vision lenses is compatibility with the Sigma Dock.
The dock, working in conjunction with the Sigma Optimization Pro software, allows the lens' firmware to be updated
(bug fixes, compatibility updates, feature enhancements, etc.) and allows precise autofocus calibration at four distances.
FTM can also be disabled/controlled via the dock.
Here are some screen grabs showing some of the functionality.

Price and Value

Not only do the Sigma 14mm and 12-24mm Art lenses share the same appearance, they also, as of review time, share the same street price.
That fact gives this 14mm Art lens another title – the most expensive Art prime lens available at this time.
While the high price will certainly limit this lens' adoption to the enthusiast and professional ranks, the unavailable-otherwise ultra-wide aperture combined with impressive image quality and solid build make this lens a reasonable value in the overall market.

The Sigma 14mm f/1.8 Art Lens is available in Canon (reviewed), Nikon, and Sigma mounts and the Canon and Sigma versions can be used on a Sony E-mount camera body via the
Sigma Mount Converter MC-11.
This lens qualifies for Sigma's Mount Conversion Service in case you later change your mind.
My standard disclaimer: There are potential issues with third party lenses.
Since Sigma reverse engineers (vs. licenses) manufacturer electronics and algorithms, there is always the possibility that a DSLR body might not support a (likely older) third party lens.
Usually a lens can be made compatible by the manufacturer via a firmware update, but this cannot be guaranteed.
Compatibility with the Sigma USB Dock is risk reducing as Sigma can make dock-compatible lens firmware updates available for download.
Sigma USA provides a 4-year limited warranty (Sigma's international limited warranty is 1 year).

The lens used for this review was obtained online/retail.

Alternatives to the Sigma 14mm f/1.8 Art Lens

As of review time, if you need a full frame lens wider than 20mm with an aperture wider than f/2.4, this lens is your only option.
Simply go buy the mount version you need.
I will not keep repeating this big Sigma advantage in the comparisons below, but keep this special attribute in mind.
If the wide aperture demands can be relinquished, the options increase.

Matching the 14mm focal length with an about-1-stop narrower aperture is the manual-focus-only Rokinon SP 14mm f/2.4 Lens.
The Sigma is sharper at f/1.8 is considerably than the Rokinon is at f/2.4.
The Rokinon approaches the Sigma's sharpness at f/4, but with the Sigma delivering amazing image quality at f/4, it is still the easy winner in this comparison.
At narrower apertures, the comparison becomes closer, but the Sigma retains the advantage, most notably in the extreme corners.

The Sigma has about 1-stop less peripheral shading at f/1.8 than the Rokinon has at f/2.4 and has nearly 2-stops less when compared at the f/2.8 aperture.
The Sigma also has considerably less flare and barrel distortion and is weather sealed.
A Rokinon advantage is light weight (27.9 vs. 41.3 oz, 791 vs. 1170g) and slightly shorter length (4.31 vs. 4.96", 109.4 vs 126mm).
The Rokinon has a longer focus ring rotation, though not everyone will find the 232° of rotation better than the Sigma's 122°.
The fact that the Rokinon is roughly half the price of the Sigma (prices fluctuate, so check the current price difference) will not be lost on most.

With a slightly narrower aperture than the Rokinon and made by the same manufacturer, the Samyang 14mm f/2.8 IF ED UMC Lens is on the radar at 14mm.
Extreme low price is this manual-aperture, manual-focus-only lens' biggest asset, but it is a great value lens.
For most aspects of this comparison, take the differences between the Sigma and the Rokinon and extend them.

The Sigma is noticeably sharper, has much less peripheral shading, considerably less flare and far less barrel distortion with a less-complicated pattern.
The Samyang weighs half as much, is considerably smaller and its focus ring has twice as much rotation.
The Samyang has only 6 aperture blades (vs. 9) and is not built as well including lack of weather sealing.
Again, bargain basement pricing is this Samyang's greatest reason for popularity.

Canon photographers will want to consider the same-brand Canon EF 14mm f/2.8L II USM Lens alternative to the Sigma 14mm Art lens.
I know, I'm starting to sound repetitive, but ... the Sigma is sharper at f/1.8 than the Canon is at f/2.8.
The two are getting more similar at f/4, but the Sigma retains the advantage.
The Sigma has noticeably less lateral CA, about 1.5 stops less peripheral shading at f/2.8, less flare and more aperture blades (9 vs. 6).
The Canon has less distortion, weighs considerably less (22.8 vs. 41.3 oz, 645g vs. 1170g) and has a higher maximum magnification (0.15x vs. 0.10x).
My AF accuracy experience was better with the Canon than the Sigma.
In this comparison, it is the Sigma that has the noticeably lower price tag.

Nikon owners will of course consider their home brand 14mm choice, the Nikon 14mm f/2.8D AF Lens.
I have not used this lens in the field, but was not impressed with the image quality the review sample delivered for us.
You guessed it, the Sigma is way sharper.
The Sigma has about 1.6 stops less peripheral shading, shows far less flare and I would rather have the Sigma's barrel distortion than the Nikon's wave/mustache pattern.
The Nikon is smaller/lighter and has a higher maximum magnification (0.15x vs. 0.10x).
The Sigma has 9 aperture blades vs. the Nikon's 6.

Nikon also make a very popular f/2.8 zoom lens that covers the 14mm focal length, the Nikon 14-24mm f/2.8G AF-S Lens.
At f/2.8, the Sigma is sharper.
But, the difference is surprisingly small for a stopped-down prime being compared to a wide open zoom.
The Sigma has less lateral CA, less vignetting, less flare and considerably less distortion than the Nikon.
These two lenses are not greatly different in size (the Nikon is slightly larger and lighter) and the Nikon again has a higher maximum magnification (0.15x vs. 0.10x).
The Nikon has the higher price tag in this case, though it offers the versatility of a zoom range.

Once again we find the Sigma winning the f/2.8 sharpness comparison versus the Irix lens, especially in the corners and the Sigma maintains some advantage at narrower apertures.
At f/2.8, the Sigma has nearly 3 stops less peripheral shading and also has less flare while the Irix has less distortion.
The manual-focus-only Irix is noticeably smaller and lighter, accepts standard (95mm) filters and has a great price tag.

The Zeiss Milvus 15 is a very impressive lens, though as of review time, I'm still trying to get a properly aligned copy of this lens.
It has the same optical design as its predecessor, the Classic version, so I'm going to refer the earlier model for this comparison.
I had and loved a Zeiss 15 for many years, but the Sigma at least equals it at f/1.8 and surpasses it at f/2.8 in terms of sharpness.
The Sigma has a nearly 3-stop peripheral shading advantage and shows slightly less flare while the Zeiss holds the distortion advantage.
The Sigma is smaller than the Zeiss (with hood) but the Zeiss is lighter.
The Sigma is well-built, but the all-metal Zeiss build is as good as it gets.
If your resources are limited, the Zeiss price is cringe-worthy.

The Tamron is the only image stabilized lens represented in this set of comparisons and that advantage should not be overlooked.
The Tamron steps aside in the image quality comparison with the prime lens turning in much sharper results than the zoom.
The Sigma has less peripheral shading (though the difference is not extreme), it has less flare and it has less distortion.
These two lenses weigh nearly the same, but the Tamron is a bit longer.
The Tamron has double the Sigma's max magnification (0.20x vs. 0.10x) and a considerably-lower price tag.

If 16mm works for you, the impressive Canon EF 16-35mm f/2.8L III USM Lens should be considered.
The Sigma vs. Canon comparison at f/2.8 is going to challenge you to pick a winner, but my eyes give the Canon zoom the edge.
At f/2.8, the Sigma has about 2.8 stops less peripheral shading.
While these two lenses have a similar amount of distortion, the Sigma has the nicer overall distortion profile.
Though similarly-sized, the Canon is lighter (27.9 vs. 41.3 oz, 790 vs. 1170g), has a considerably-higher maximum magnification (0.25x vs. 0.10x), accepts standard threaded filters and has the zoom range versatility advantage.
My AF accuracy experience is considerably better with the Canon than the Sigma.

Summary

So, is the Sigma 14mm f/1.8 Art Lens the best wide field astrophotography lens?
Yes, as of review time, I think it is.
As popular as astrophotography is, I'm surprised by the lack of standout wide field lenses available for this purpose.
The 14 Art's corners are not perfect, but with excellent wide open image sharpness and a low amount of peripheral shading, this lens gets my vote as the best choice for capturing the night sky.

Easy to say is that this is the best 14mm f/1.8 DSLR lens ever produced, as there has never been another.
Not hard to argue is that the Sigma 14mm f/1.8 Art Lens has the best 14mm image quality available to date.
This lens delivers impressively sharp images, ranking very high in the entire field of lenses (not just among its ultra-wide peers).
The design of this lens is aesthetically pleasing and the build quality similarly-good.
The price will set you back a noticeable amount and the AF system may not leave you impressed, but the other aspects of this lens will make it a top choice for fulfilling the critical ultra-wide angle needs in many serious kits.
Prepare to say "Wow!" when reviewing your images.

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